42 ELECTRICALCONTRACTOR | OCT. 14 | WWW.ECMAG.COM
QUIZ BY JIM HAYES
The Language of Fiber Optics
Every technical subject has its own set of special terms and abbreviations. Unless you understand
them, you will find it hard to read about or discuss the technology. Most people know the basic
“language of fiber optics,” but some common terms, like dB, are often confused. ANSWERS ARE ON
PAGE 111. TO TAKE THE QUIZ IN AN ELECTRONIC FORMAT, VISIT WWW.ECMAG.COM.
1. The decibel (dB) was named for Alexander Graham Bell,
who first used it for measuring __________, a common use
C. Telephone amplifiers
2. Decibels are used for measuring power on a __________ scale.
3. We measure optical power in both dB and decibel-milliwatts (dBm). Which of the following statements
about dBm is true?
A. dBm is absolute power, like a transmitter’s output.
B. dBm is absolute power relative to 1 milliwatt of power.
C. The difference between two measurements
in dBm is expressed in dB.
D. All of these statements are true.
4. The attenuation coefficient of an optical fiber is expressed
C. dB per kilometer (dB/km)
5. The total loss of a fiber optic cable plant is expressed
6. If you measure a fiber optic cable plant with a loss of 3 dB,
the light exiting at the end of the fiber will be __________ as
powerful as the light entering the fiber.
7. If you measure a fiber optic cable plant with a loss of 10 dB,
the light exiting at the end will be __________ as powerful as
the light entering the fiber.
8. Fiber optic power meters have buttons to choose dB or dBm
readings and the wavelength because the meter detector
varies sensitivity with wavelength.
9. The dBm scale of a fiber optic power meter reads absolute
power referenced to 1 milliwatt of power, so it must be
calibrated to __________ standards to confirm its accuracy.
A. Telecommunications Industry Association
B. International Organization for Standardization
C. Department of Defense
D. National Institute of Standards and Technology
10. Most fiber optic communications systems operate in the
range of __________.
A. 0 to + 30 dBm
B. + 10 to – 30 dBm
C. – 20 to – 60 dBm
D. +/– 3 dB
HAYES is a VDV writer and educator and the president of The Fiber Optic Association. Find him at www.Jim Hayes.com.